Wow, I'm kind of the opposite of all you guys. XD
I really liked Mixi when I started. I purposefully went on there as a way to improve my Japanese. I met a lot of "strangers", Japanese and non-Japanese (some of them don't understand Any Japanese which, I didn't understand but..). Most of the Japanese wanted to practice English, a handful wanted to help Me improve, and a very few wanted to practice one of the other languages I was learning. Some of the non-Japanese I met because of music interests and we would talk about school, or how our countries are different, etc.
Everyone would post diary entries too, so if you weren't connecting through a message, it was through endless replies on their diary. But I guess we all caught (or I caught all of them) at a good time then, because now only 2 or 3 people post diaries, no one sends messages anymore and if you do, it takes so long for a reply; like if everyone just got busy (or maybe it's all on me?). The things I see mostly updated now are just communities. I mean I know I can jump start my social life on there again, but Mixi right now does no good for my present situation and would actually stress me out~ so =/ I'd feel bad for whoever was trying to respark with me and I had no time to reply. And I do have friends on there who I do know in 'real life', but I sort of liked it how I could practice and not have anyone I know see my mistakes. I guess I was using it as an escape? lol
So I know its true what Elec said about it mostly being for Japanese people to keep in touch with friends, but it doesn't mean you can't thrive as a foreigner. And I think the communities serve as meeting strangers period. And I do believe that some of non-Japanese I made contact with Work in Japan, or study in Japan, so ... more connections?
Oh, and I Love ashiato.
But if it was put on myspace or facebook, i would get SO MAD.